Multifunctional Action Site Strategy of a Buried Interface for High-Performance Perovskite Solar Cells

The buried interface is pivotal for enhancing both the efficiency and stability of p-i-n perovskite solar cells (PSCs). This is because carrier extraction and recombination processes can be significantly affected by the defects that tend to form on the bottom side. Herein, a dual-reaction site molecule homopiperazine-1,4-bis (2-ethanesulfonic acid) (HEA) is employed as an effective multifunctional passivator for a self-assembled monolayer (SAM)/perovskite interface for the inverted PSCs. The HEA molecule has two sulfonic acid groups with double action sites, which can effectively fill the ITO vacancies unanchored by SAM and simultaneously passivate the uncoordinated Pb²⁺ defects of perovskite to form an effective molecular bridge, achieving full coverage of the substrate and orderly crystallization of perovskites. The resultant device presented satisfactory efficiencies of 25.71% (0.0982 cm²) and 24.26% (1 cm²). Our device retained 91.8% of its initial power conversion efficiency (PCE) after 1000 h of operation under 1-sun illumination in a nitrogen atmosphere. This research offers important insights into further refinement and enhancement of buried interfaces in PSCs.